The present invention is an electrical outlet or junction box designed to prevent air interchange through the box between room and wall space.
One beneficial side effect of the drastic increase in energy costs of the past decade has been the increased emphasis on energy conservation. This has perhaps been most visible in transportation related industries where dramatic improvements have been made. However, improvements of equal magnitude have been made in many commercial, industrial, and residential buildings. If residential buildings can be taken as an example, building codes in many areas now require energy saving measures such as full wall and ceiling insulation, and double or triple pane window glass. Many innovative builders have adopted measures for energy conservation that go well beyond any required by building codes.
The major portion of heat lost from a building occurs by conduction through walls and ceilings when the interior temperature is higher than the outside environment. During the summer months, when air conditioning is frequently used, the opposite situation will prevail and the major source of heat entry will be through walls and ceilings. However, a very significant amount of energy loss occurs by convective air interchange between the interior and outside of a building. In some newer structures that are very well insulated the conductive losses have been reduced to the point that convective losses comprise the majority of the heat loss. Weather stripping around doors and windows has been used for many years and is an effective way of reducing air interchange. Many other entry points for outside air are not so well rcognized. As one example, relatively few builders caulk or seal the area between mud sills and foundation even though this is a major point of air interchange. Any opening cut into an inside wall provides another access point for cold winter or warm summer outside air. Openings for electrical outlet or junction boxes are prime zones for this type of air interchange.
Energy conscious builders today have gone to measures to reduce air interchange that would have been almost unthinkable even a decade ago. One of these is the use of polyolefin vapor barrier films placed under the typical gypsum board or "Sheetrock" used on interior walls. Conscientious builders will even attempt to seal electrical outlet boxes to this barrier film to insure absolutely tight construction. Unfortunately, outlet boxes have remained essentially unchanged for many years and have not evolved to accommodate this new demand which is now being placed upon them. Most of them are ill adapted for forming a tight seal that would prevent air flow through them.
A few inventors have recognized the above problem and attempted to deal with it. Balkwill et al. in U.S. Pat. Nos. 4,296,870 and 4,345,693 show a flanged plastic outer cover for an outlet box. The flanges, which may be made in accordion fashion, press against the back of the Sheetrock to form a seal. These plastic covers are made of light gauge material, typically about 1 mm in thickness. Nails can be readily driven through them so that the outlet boxes may be mounted conventionally. The inventors note that holes may be readily punched through the plastic outer box to allow entry of wires or cables into the junction box. Optionally, the area where these wires enter may be caulked.
Other builders have attempted to caulk around wire entry points and in the gap or juncture between the outside of the junction box and the adjacent Sheetrock. Similarly, before Sheetrock is applied, some builders using polyolefin barrier film will attempt to seal around electrical outlet boxes using a caulking material or duct tape. To date these measures have not been particularly satisfactory since they tend to be relatively slow and are frequently ineffective. As one example, it is extremely difficult to place an effective caulk seal around the entry point of a wire into a conventional outlet box. The necessary access to the area is marginal under the best conditions. There is a second problem as well. The edge of the junction box at the point of wire entry is quite thin and does not effectively retain most caulking compounds. Typically, they will sag or run by the action of gravity so that they flow out of the opening being sealed unless excessively large amounts are used.
Other earlier United States patents which have some structural relationship to the present invention but which were not attempts to solve the present problem are Maier, U.S. Pat. No. 4,103,101; Boteler, U.S. Pat. No. 4,265,365; and Slater et al. U.S. Pat. No. 4,389,535.
The electrical outlet box of the present invention overcomes the above problems and is well adapted for use on walls where a sealed, airtight construction is desired. It is particularly well adapted to the very recent approach to air tight construction in which the Sheetrock itself is sealed by caulking and the use of low air permeability paints.